209409481 has 2 divisors, whose sum is σ = 209409482. Its totient is φ = 209409480.

The previous prime is 209409443. The next prime is 209409521. The reversal of 209409481 is 184904902.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 172685881 + 36723600 = 13141^2 + 6060^2 .

It is a cyclic number.

It is not a de Polignac number, because 209409481 - 2¹⁷ = 209278409 is a prime.

It is a super-2 number, since 2×209409481² = 87704661465378722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 209409481.

It is not a weakly prime, because it can be changed into another prime (209406481) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104704740 + 104704741.

It is an arithmetic number, because the mean of its divisors is an integer number (104704741).

Almost surely, 2^209409481 is an apocalyptic number.

It is an amenable number.

209409481 is a deficient number, since it is larger than the sum of its proper divisors (1).

209409481 is an equidigital number, since it uses as much as digits as its factorization.

209409481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 209409481 is about 14470.9875613242. The cubic root of 209409481 is about 593.8345295572.

The spelling of 209409481 in words is "two hundred nine million, four hundred nine thousand, four hundred eighty-one".